The present invention relates generally to turbine engines and more particularly to methods and apparatus for securing blades used within turbine engines.
At least some known turbine rotor assemblies include a rotor to which a plurality of blades are coupled. The blades are arranged in axially-spaced stages extending circumferentially around the rotor. Each stage includes a set of stationary blades or nozzles, and a set of cooperating rotating blades, known as buckets.
Each bucket includes a dovetail that is used to couple the bucket to an annular slot defined by the rotor. More specifically, each dovetail includes a recessed portion, know as a hook, that is defined by axial tangs and that enables each blade to be slidably coupled to the rotor.
Each rotor slot is defined by a pair of substantially parallel retaining rings. During assembly, a first bucket dovetail is inserted into the retaining rings through a loading slot defined within the retaining rings. Adjacent buckets are also coupled to the rotor through the loading slot and slid circumferentially into position. The last bucket, known as the closure bucket, is coupled to the rotor and remains within the loading slot. All of the buckets, with the exception of the closure bucket, are coupled to the rotor by the retaining ring. Known closure buckets are coupled in position within the loading slot by a pair of shear pins which are inserted axially between the closure bucket and the circumferentially adjacent buckets. However, some rotors do not permit axial insertion of shear pins due to close stage to stage spacing.